Low-Cost Desalination for Seawater and Hybersaline Brine Using Nanophotonics Enhanced Solar Energy Membrane Distillation
A stand-alone small-scale Nanophotonics Enhanced Solar Membrane Distillation (NESMD) testbed was designed, developed, and tested for desalinating seawater and high salinity feedwaters. This NESMD system can take almost any source water, and turn it into clean water with sunlight as the only energy source. The NESMD technology applies nanophotonic coating materials on commercial hydrophobic Polypropylene support of a Polytetrafluoroethylene (PTFE) membrane surface. The photothermal coating serves as a solar-thermal collector, absorbs solar energy, and generates highly localized heat on the membrane, while the rest of the membrane performs the membrane distillation function. The presented NESMD system is equipped with an internal heat recovery system with no need for external electricity and no additional water for cooling. The NESMD testbed is installed and tested at Rice University campus (29.7174° N, 95.4018° W). In this study, real seawater from Galveston Bay, Texas U.S., and high salinity simulated feedwaters (total dissolved solids (TDS) 113,200– 200,000 PPM) have been tested for long-term testing in the weather conditions of Houston, Texas. The field testing results showed a stable desalination performance in consecutive 5-8 hour operation cycles, with TDS removal 99.5% in all experiments. Average daily membrane flux of 0.75 L/m2-hr was achieved at a solar intensity close to 1 kW/m2 without an external heat exchanger. Further investigations and improvements are required to enhance the performance of the reactor since it is still a new promising technology.